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A total of 16 male cases with malignant tumours associated with arsenic-polluted water were observed in Tarapacá and Antofagasta Provinces, northern Chile. Fifteen of them had skin carcinomata and the remaining one a hemangio-endothelioma of liver. The skin cancer cases had latent periods ranging from 12-45 years. Three patients were studied in detail. The first one (skin cancer) had a latent period of 20 years with a weighted mean dose of 1.2 mg/day (total dose for latent period 8.4 g). The second one (skin cancer) had a latent period of 23 years with a weighted mean dose of 1.0 mg/day (total dose for latent period 8.3 g). The third case (liver tumour) exhibited a latent period of 14 years with a weighted mean of 0.6 mg/day (total dose for latent period 3.1 g). Fifteen of the 16 cancer patients were labourers. For normal subjects of different ages and both sexes (n = 290) and ingesting arsenic-polluted water (0.60 ppm), the relationship between mean age and mean arsenic dose is expressed by a weighted least square polynomial regression, of second degree: E(y)- beta 0 + beta 1t + beta 2 t2 where y is mean arsenic dose (mg/person/day) and t is mean age (years). For the general male population and for male labourers, the respective equations are presented.

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Since a significant positive correlation between nitrate fertilizer exposure and stomach cancer mortality has been found, a study of nitrate fertilizer pollution in arable land in terms of amount of nitrates used per unit area (kg/ha) and stomach cancer death rates was carried out. The regression of death rates for stomach cancer, standardized for age, on the nitrates used per unit area, by province (N = 25), exhibited a significant association between the 2 variables (p less than 0.004). When industrialized provinceds (N = 3) were not considered, a highly significant association was found (F = 16.47; d.f. = 1, 20; p less than 0.0006). The correlation coefficient was + 0.672.

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